数据库管理 毕业论文外文资料翻译.doc

毕业设计(论文)外文资料翻译学生姓名： 学 号： 所在学院： 电子与信息工程学院 专 业： 计算机科学与技术 指导教师： 2011年 12月 25 日english data original texttranslates the foreign materials: author: feras t.dabous book title (or paper topic): database management publishing house (or publication name): http:/ /china/database/default.mspx publication time (or registration number): july 2004database managementdatabase (sometimes spelled database) is also called an electronic database, referring to any collections of data, or information, that is specially organized for rapid search and retrieval by a computer. databases are structured to facilitate the storage, retrieval modification and deletion of data in conjunction with various data-processing operations. database can be stored on magnetic disk or tape, optical disk, or some other secondary storage device.a database consists of a file or a set of files. the information in the these files may be broken down into records, each of which consists of one or more fields are the basic units of data storage, and each field typically contains information pertaining to one aspect or attribute of the entity described by the database. using keywords and various sorting commands, users can rapidly search, rearrange, group, and select the fields in many records to retrieve or create reports on particular aggregates of data.database records and files must be organized to allow retrieval of the information. early system were arranged sequentially (i.e., alphabetically, numerically, or chronologically); the development of direct-access storage devices made possible random access to data via indexes. queries are the main way users retrieve database information. typically the user provides a string of characters, and the computer searches the database for a corresponding sequence and provides the source materials in which those characters appear. a user can request, for example, all records in which the content of the field for a persons last name is the word smith.the many users of a large database must be able to manipulate the information within it quickly at any given time. moreover, large business and other organizations tend to build up many independent files containing related and even overlapping data, and their data, processing activities often require the linking of data from several files. several different types of database management systems have been developed to support these requirements: flat, hierarchical, network, relational, and object-oriented. in flat databases, records are organized according to a simple list of entities; many simple databases for personal computers are flat in structure. the records in hierarchical databases are organized in a treelike structure, with each level of records branching off into a set of smaller categories. unlike hierarchical databases, which provide single links between sets of records at different levels, network databases create multiple linkages between sets by placing links, or pointers, to one set of records in another; the speed and versatility of network databases have led to their wide use in business. relational databases are used where associations among files or records cannot be expressed by links; a simple flat list becomes one table, or “relation”, and multiple relations can be mathematically associated to yield desired information. object-oriented databases store and manipulate more complex data structures, called “objects”, which are organized into hierarchical classes that may inherit properties from classes higher in the chain; this database structure is the most flexible and adaptable.the information in many databases consists of natural-language texts of documents; number-oriented database primarily contain information such as statistics, tables, financial data, and raw scientific and technical data. small databases can be maintained on personal-computer systems and may be used by individuals at home. these and larger databases have become increasingly important in business life. typical commercial applications include airline reservations, production management, medical records in hospitals, and legal records of insurance companies. the largest databases are usually maintained by governmental agencies, business organizations, and universities. these databases may contain texts of such materials as catalogs of various kinds. reference databases contain bibliographies or indexes that serve as guides to the location of information in books, periodicals, and other published literature. thousands of these publicly accessible databases now exist, covering topics ranging from law, medicine, and engineering to news and current events, games, classified advertisements, and instructional courses. professionals such as scientists, doctors, lawyers, financial analysts, stockbrokers, and researchers of all types increasingly rely on these databases for quick, selective access to large volumes of information.1dbms structuring techniquessequential, direct, and other file processing approaches are used to organize and structure data in single files. but a dbms is able to integrate data elements from several files to answer specific user inquiries for information. that is, the dbms is able to structure and tie together the logically related data from several large files. logical structures. identifying these logical relationships is a job of the data administrator. the dbms may then employ one of the following logical structuring techniques during storage access, and retrieval operations.list structures. in this logical approach, records are linked together by the use of pointers. a pointer is a data item in one record that identifies the storage location of another logically related record. records in a customer master file, for example, will contain the name and address of each customer, and each record in this file is identified by an account number. during an accounting period, a customer may buy a number of items on different days. thus, the company may maintain an invoice file to reflect these transactions. a list structure could be used in this situation to show the unpaid invoices at any given time. each record in the customer in the invoice file. this invoice record, in turn, would be linked to later invoices for the customer. the last invoice in the chain would be identified by the use of a special character as a pointer.hierarchical (tree) structures. in this logical approach, data units are structured in multiple levels that graphically resemble an “upside down” tree with the root at the top and the branches formed below. theres a superior-subordinate relationship in a hierarchical (tree) structure. below the single-root data component are subordinate elements or nodes, each of which, in turn, “own” one or more other elements (or none). each element or branch in this structure below the root has only a single owner. thus, a customer owns an invoice, and the invoice has subordinate items. the branches in a tree structure are not connected.network structures. unlike the tree approach, which does not permit the connection of branches, the network structure permits the connection of the nodes in a multidirectional manner. thus, each node may have several owners and may, in turn, own any number of other data units. data management software permits the extraction of the needed information from such a structure by beginning with any record in a file.relational structures. a relational structure is made up of many tables. the data are stored in the form of “relations” in these tables. for example, relation tables could be established to link a college course with the instructor of the course, and with the location of the class.to find the name of the instructor and the location of the english class, the course/instructor relation is searched to get the name (“fitt”), and the course/location relation is a relatively new database structuring approach thats expected to be widely implemented in the future.physical structures. people visualize or structure data in logical ways for their own purposes. thus, records r1 and r2 may always be logically linked and processed in sequence in one particular application. however, in a computer system its quite possible that these records that are logically contiguous in one application are not physically stored together. rather, the physical structure of the records in media and hardware may depend not only on the i/o and storage devices and techniques used, but also on the different logical relationships that users may assign to the data found in r1and r2. for example, r1 and r2 may be records of credit customers who have shipments send to the same block in the same city every 2 weeks. from the shipping department managers perspective, then, r1 and r2 are sequential entries on a geographically organized shipping report. but in the a/r application, the customers represented by r1 and r2 may be identified, and their accounts may be processed, according to their account numbers which are widely separated. in short, then, the physical location of the stored records in many computer-based information systems is invisible to users. 2database management features of oracle oracle includes many features that make the database easier to manage. weve divided the discussion in this section into three categories: oracle enterprise manager, add-on packs, backup and recovery.2.1 oracle enterprise manageras part of every database server, oracle provides the oracle enterprise manager (em), a database management tool framework with a graphical interface used to manage database users, instances, and features (such as replication) that can provide additional information about the oracle environment.prior to the oracle8i database, the em software had to be installed on windows 95/98 or nt-based systems and each repository could be accessed by only a single database manager at a time. now you can use em from a browser or load it onto windows 95/98/2000 or nt-based systems. multiple database administrators can access the em repository at the same time. in the em repository for oracle9i, the super administrator can define services that should be displayed on other administrators consoles, and management regions can be set up.2.2 add-on packsseveral optional add-on packs are available for oracle, as described in the following sections. in addition to these database-management packs, management packs are available for oracle applications and for sap r/3.(1) standard management pack the standard management pack for oracle provides tools for the management of small oracle databases (e.g., oracle server/standard edition). features include support for performance monitoring of database contention, i/o, load, memory use and instance metrics, session analysis, index tuning, and change investigation and tracking.(2) diagnostics pack you can use the diagnostic pack to monitor, diagnose, and maintain the health of enterprise edition databases, operating systems, and applications. with both historical and real-time analysis, you can automatically avoid problems before they occur. the pack also provides capacity planning features that help you plan and track future system-resource requirements. (3) tuning packwith the tuning pack, you can optimise system performance by identifying and tuning enterprise edition databases and application bottlenecks such as inefficient sql, poor data design, and the improper use of system resources. the pack can proactively discover tuning opportunities and automatically generate the analysis and required changes to tune the systems. (4) change management packthe change management pack helps eliminate errors and loss of data when upgrading enterprise edition databases to support new applications. it impact and complex dependencies associated with application changes and automatically perform database upgrades. users can initiate changes with easy-to-use wizards that teach the systematic steps necessary to upgrade.(5) availabilityoracle enterprise manager can be used for managing oracle standard edition and/or enterprise edition. additional functionality is provided by separate diagnostics, tuning, and change management packs.2.3 backup and recoveryas every database administrator knows, backing up a database is a rather mundane but necessary task. an improper backup makes recovery difficult, if not impossible. unfortunately, people often realize the extreme importance of this everyday task only when it is too late usually after losing business-critical data due to a failure of a related system.the following sections describe some products and techniques for performing database backup operations.(1) recovery managertypical backups include complete database backups (the most common type), database backups, control file backups, and recovery of the database. previously, oracles enterprise backup utility (ebu) provided a similar solution on some platforms. however, rman, with its recovery catalog stored in an oracle database, provides a much more complete solution. rman can automatically locate, back up, restore, and recover databases, control files, and archived redo logs. rman for oracle9i can restart backups and restores and implement recovery window policies when backups expire. the oracle enterprise manager backup manager provides a gui-based interface to rman.(2) incremental backup and recoveryrman can perform incremental backups of enterprise edition databases. incremental backups back up only the blocks modified since the last backup of a datafile, tablespace, or database; thus, theyre smaller and faster than complete backups. rman can also perform point-in-time recovery, which allows the recovery of data until just prior to a undesirable event.(3) legato storage managervarious media-management software vendors support rman. oracle bundles legato storage manager with oracle to provide media-management services, including the tracking of tape volumes, for up to four devices. rman interfaces automatically with the media-management software to request the mounting of tapes as needed for backup and recovery operations.(4) availabilitywhile basic recovery facilities are available for both oracle standard edition and enterprise edition, incremental backups have typically been limited to enterprise edition.外文资料中文译文所译外文资料： 作者：feras t.dabous 书名（或论文题目）：数据库管理 出版社（或刊物名称）：http:/ /china/database/default.msp 出版时间（或刊号）：july 2004数据库管理数据库（有时拼成database）也称为电子数据库，是指由计算机特别组织的用下快速查找和检索的任意的数据或信息集合。数据库与其它数据处理操作协同工作，其结构要有助于数据的存储、检索、修改和删除。数据库可存储在磁盘或磁带、光盘或某些辅助存储设备上。一个数据库由一个文件或文件集合组成。这些文件中的信息可分解成一个个记录，每个记录有一个或多个域。域是数据库存储的基本单位，每个域一般含有由数据库描述的属于实体的一个方面或一个特性的信息。用户使用键盘和各种排序命令，能够快速查找、重排、分组并在查找的许多记录中选择相应的域，建立特定集上的报表。数据库记录和文件的组织必须确保能对信息进行检索。早期的系统是顺序组织的（如:字母顺序、数字顺序或时间顺序）；直接访问存储设备的研制成功使得通过索引随机访问数据成为可能。用户检索数据库信息的主要方法是query（查询）。通常情况下，用户提供一个字符串，计算机在数据库中寻找相应的字符序列，并且给出字符串在何处出现。比如，用户必须能在任意给定时间快速处理内部数据。而且，大型企业和其它组织倾向于建立许多独立的文件，其中包含相互关联的甚至重叠的数据，这些数据、处理活动经常需要和其它文件的数据相连。为满足这些要求，开发邮各种不同类型的数据库管理系统，如：非结构化的数据库、层次型数据库、网络型数据库、关系型数据库、面向对象型数据库。在非结构化的数据库中，按照实体的一个简单列表组织记录；很多个人计算机的简易数据库是非结构的。层次型数据库按树型组织记录，每一层的记录分解成更小的属性集。层次型数据库在不同层的记录集之间提供一个单一链接。与此不同，网络型数据库在不同记录集之间提供多个链接，这是通过设置指向其它记录集的链或指针来实现的。网络型数据库的速度及多样性使其在企业中得到广泛应用。当文件或记录间的关系不能用链表达时，使用关系型数据库。一个表或一个“关系”，就是一个简单的非结构列表。多个关系可通过数学关系提供所需信息。面向对象的数据库存储并处理更复杂的称为对象的数据结构，可组织成有层次的类，其中的每个类可以继承层次链中更高一级类的特性，这种数据库结构最灵活，最具适应性。很多数据库包含自然语言文本信息，可由个人在家中使用。小型及稍大的数据库在商业领域中占有越来越重要的地位。典型的商业应用包括航班预订、产品管理、医院的医疗记录以及保险公司的合法记录。最大型的数据库通常用天政府部门、企业、大专院校等。这些数据库存有诸如摘要、报表、成文的法规、通讯录、报纸、杂志、百科全书、各式目录等资料。索引数据库包含参考书目或用于找到相关书籍、期刊及其它参考文献的索引。目前有上万种可公开访问的数据库，内容包罗万象，从法律、医学、工程到新闻、时事、游戏、分类广告、指南等。科学家、医生、律师、财经分析师、股票经纪人等专家和各类研究者越来越多地依赖这些数据库从大量的信息中做快速的查找访问。1数据库管理系统的组织技术顺序的、直接的以及其他的文件处理方式常用于单个文件中数据的组织和构造，而dbms可综合几个文件的数据项以回答用户对信息的查询，这就意味着dbms能够访问和检索非关键记录字段的数据，即dbms能够将几个大文件夹中逻辑相关的数据组织并连接在一起。逻辑结构：确定这些逻辑关系是数据管理者的任务，由数据定义语言完成。dbms在存储、访问和检索操作过程中可选用以下逻辑构造技术：链表结构：在该逻辑方式中，记录通过指针链接在一起。指针是记录本中的一相数据项，它指出另一个逻辑相关的记录的存储位置，例如，顾客主文件中的记录将包含每个顾客的姓名和地址，而且该文件中的每个记录都由一个账号标识。在记账期间，顾客可在不同时间购买许多东西。公司保存一个发票文件以反映这下地交易，这种情况下可使用链表结构，以显示给定时间内未支付的发票。顾客文件中的每个记录都包含这样一个字段，该字段指向发票文件中该顾客的第一个发票的记录位置，该发票记录又依次与该顾客的下一个发票记录相连，此链接的最后一个发票记录由一个作为指针的特殊字符标识。层次（树型）结构：该逻辑方式中，数据单元的多级结构类似一棵“倒立”的树，该树的树根在顶部，而树枝向下延伸。在层次（树型）结构中存在主-从关系，惟一的根数据下是从属的元或节点，而每个元或树枝都只有一个所有者，在树型结构中，树枝不能相连。网状结构：网状结构不像树型结构那样不允许树枝相连，它允许节点间多个方向连接，这样，每个节点都可能有几个所有者，中央电视台它又可能拥有任意多个其他数据单元。数据管理软件允许从文件的任一记录开始提取该结构中的所需信息。关系型结构：关系型结构由许多表格组成，数据则以“关系”的形式存储在这些表中。例如，可建立一些关系表，将大学课程同任课教师及上课地点连接起来。为了找到英语课的上课地点和教师名，首先查询课程/教师关系表得到名字（为“fitt”），再查询课程/地点关系表得到地点（“main 142”），当然，也可能有其他关系。这是一个相当新颖的数据库组织技术，将来有望得到广泛应用。物理结构：人们总是为了各自的目的，按逻辑方式设想或组织数据。因此，在一个具体应用中，记录r1和r2是逻辑相连且顺序处理的，但是，在计算机系统中，这些在一个应用中逻辑相邻的记录，物理位置完全可能不在一起。记录在介质和硬件中的物理结构不仅取决于所采用的i/o设备、存储设备